Release of indomethacin from tabletted ethylcellulose microcapsules

Abstract

Indomethacin was microencapsulated in a coacervation process using ethylcellulose as a wall material and polyisobutylene as a coacervation inducing agent. Micronized sodium chloride was added as a pore former into the microcapsule wall. Microcapsules were tabletted with plastically deforming microcrystalline cellulose and fragmenting dicalcium phosphate as well as with their binary mixture. The effect of compression pressure on drug release was evaluated. The release of indomethacin was also studied after effective disintegration of the tablets by crosslinked sodium carboxymethylcellulose. Release of indomethacin from plain microcapsules accelerated markedly when sodium chloride was added in the microcapsule wall. All the tablets without disintegrant stayed nearly intact during the dissolution test. The tablets of microcapsules were composed of a porous ethylcellulose matrix in which the microcapsules were separated from each other by easily wettable tablet adjuvants. The drug release accelerated from the tablets due to the mechanical destruction of microcapsule wall, which was more clearly seen after disintegration of the tablets to the multiple microcapsule units. The rupture of microcapsule films was most extensive with the tablets containing fragmenting dicalcium phosphate as a filler. The addition of sodium chloride in the microcapsule wall seemed to make the polymer film firmer thus reducing the destructive effect of tablet adjuvants.